1. Technical Field
The present invention relates to an image display apparatus and a control method thereof, in which the image display apparatus receives an input of a video signal and displays an image based on the video signal.
2. Related Art
Generally, in an image display apparatus that displays an image by making phosphors to emit light with use of indicating elements, such as CRT (Cathode Ray Tube) and PDP (Plasma Display Panel), there is provided an automatic brightness limiter circuit (hereinafter referred to as “ABL circuit”) in order to prevent problems arising out of high-brightness image display, such as the deterioration of display quality (image distortion) caused by high-voltage fluctuation and the degradation of indicating elements caused by heat generation (See JP-A-59-111489, JP-A-2-90788, JP-A-5-7350, JP-A-11-27602, JP-A-2000-75833, JP-A-2000-242212, and JP-A-2002-372943). The ABL circuit makes a correction for a video signal to limit the emission brightness of indicating elements when APL (Average Picture Level) of an inputted video signal is higher than a predetermined level.
On the other hand, in an image display apparatus that produces an image by modulating the light emitted from a light source with use of indicating elements such as LCD (liquid crystal display) and DMD (registered trademark) (Digital Micromirror Device), there is no deterioration of display quality (image distortion) arising out of high brightness. Hence, such an image display apparatus does not require an ABL circuit. In actuality, general image displays do not have an ABL circuit.
Such an image display apparatus that does not include an ABL circuit, however, has a problem that it gives a viewer stronger glare compared to the case of CRT or the like when an image is displayed based on a video signal having a high APL, causing the viewer discomfort. Particularly, a television commercial and the like are often constructed with stimulative and bright images so as to attract viewers attention even with use of CRT or the like having an ABL circuit, so that such images tend to have a higher APL. Further, the use of a large size screen or a dark viewing environment gives a viewer stronger glare, too.
On the other hand, in an image display apparatus having an ABL circuit, the ABL circuit restrains the above-referenced glare. However, the ABL circuit inevitably performs the function even for image works including a lot of visual stage effects, such as movie pictures. Therefore, there is still a problem that the above-referenced image display apparatus with an ABL circuit can not reproduce image expressions faithfully to producer's intention.